EPOW - Ecology Picture of the Week

Cactus in the Lava Fields

Lava Cactus (Brachycereus nesioticus), Family Cactaceae
Galapagos Islands, Ecuador

Explanation:  This is tough hiking, here on along Punta Espinosa on Fernandina Island of the Galapagos Islands of Ecuador.  

Watch out for the uneven, sharp-edged "aa" lava with all the pits and slopes, and then watch out for the cactus, growing here, somehow, straight from the rock itself.

This is, in fact, a species of cactus found only on the Galapagos Islands and nowhere else in the world.  This is the aptlly-named lava cactus.  

Lava cactus is a pioneer species, which means that it's one of the first plants to colonize the otherwise plant-less, barren lava fields.  This is primary succession at its finest.  

Lava cactus doesn't form a branching structure and stays low and close to the ground, perhaps illustrating a stunted growth form because of the dearth of nutrients and water found in this volcanic world.  

Young stems tent to be greenish-yellow but turn gray to black over time.  
  

A youthful cactus has taken hold of its place in the sun.

      

 

This cluster is a bit older,
showing the gray and black
color of advancing age.